Journal bearing

ABSTRACT

A journal bearing for a rotating mass, wherein a lubricating fluid is disposed in a bearing cavity defined between an inner bearing member and an outer bearing member. One of the bearing surfaces is provided with at least two sets of grooves, the grooves of each set adapted to impel said fluid axially with respect to said cavity towards a common point.

United States Patent 2,479,349 8/l949 Hagg inventor Harvey HandlerWayne, NJ.

Sept. 18, 1969 Aug. 31, 1971 Singer-General Precision, Inc. LittleFalls, NJ.

Appl. No. Filed Patented Assignee JOURNAL BEARING 2 Claims, 5 DrawingFigs.

US. Cl 308/9 Int. Cl. Fl6c 17/02 Field of Search 308/9, 12],

References Cited UNITED STATES PATENTS 3,439,962 4/1969 Gothberg 308/9FOREIGN PATENTS 585,864 2/1947 GreatBritain; 308/240 OTHER REFERENCESProduct Engineering, page 386, Jul. 1942 copy in class 308/240 PrimaryExaminer-Martin P. Schwadron Assistant Examiner Frank Susko Attorneys-S.A. Giarratana and M. Bender F V/// 4/ iii 14 fist-55:1 /0 g A mPATENTEDAUB31 am 3502 .555

IMRVEV A/ENOZER INVENTOR.

JOURNAL BEARING BACKGROUND or THE INVENTION This invention relates to ajournal bearing and, more particularly, to such a bearing having atleast two sets of grooves formed in one of the cooperating surfaces ofan outer bearing member and an inner bearing member separated by a fluidlubricant.

Grooved journal bearings are generally known, and normally feature theuse of a single set of grooves formed in the outer surface of a journalwhich extends within a liquid reservoir extending between it and itsstator. Therefore, when the journal is rotated with respect to thestator, the stability of the bearing is increased with no sacrifice inload capacity since the outer grooves are arranged so that they act likea pump as the journal turns, forcing fluids from the ends of the groovedbearing towards the middle thereof.

However, these arrangements suffer since the radial stiffness in thegrooved bearing is not constant throughout the length of the bearing,but rather increases towards the center thereof. Therefore, for a givenapplied external force, such as that caused by the drive motor for thejournal, for example, the journal will deflect about a node point andcause an external reaction along various portions of the journal. Thisis extremely undesirable in certain applications, such as in the use ofgyroscopes having a sensitive point at its hinge center, since thesereactions will result in drift.

SUMMARY OF THE INVENTION It is therefore an object of the presentinvention to provide a grooved journal bearing in which the reactionforce acting on the bearing is more evenly distributed over the lengthof the journal, thereby eliminating any unnecessary external forcesacting along the journal.

This object is achieved according to the bearing of the presentinvention which comprises an inner bearing member, an outer bearingmember extending coaxially with said inner bearing member, the innersurface of said outer bearing member being spaced from the outer surfaceof said inner bearing member to define acylindrical bearing cavity, alubricating fluid disposed in said cavity, at least one of said surfacesbeing provided with at least two sets of grooves, the grooves of eachset adapted to impel said fluid axially with respect to said cavitytowards a common point to form at least two points of maximum stiffnessalong said journal. BRIEF DESCRIPTION OF THE DRAWINGS Reference is nowmade to the accompanying drawings for a better understanding of thenature and objects of the present invention. The drawings illustrate thebest mode presently contemplated for carrying out the objects of theinvention and are not to be construed as restrictions or limitations onits scope. In the drawings:

FIG. I is a fragmentary elevational view of a typical prior artarrangement of a rotor stator;

FIG. 2 is an elevational view of a grooved journal according to a priorart arrangement;

FIG. 3 is a perspective view depicting a grooved journal according tothe present invention;

FIG. 4 is a view similar to FIG. 2 but showing the. grooved journal ofthe present inventiomand FIG. 5 is a view similar to FIG. 4 but showinganother embodiment of the grooved journal of the present invention.DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 of the drawings depictsa typical environment for a journal bearing, and includes a journaldisposedin a fixed stator 12, with a fluid such as gas or the likedisposed in the bearing cavity defined between'the outer surface of thejournal and the inner surface of the stator.

According to some known arrangements, the journal 10 is grooved in amanner shown better with reference toFIG. 2. Specifically, a single setof grooves 16 are formed in thejournal l0 and are arranged so that thefluid in the bearing cavity I will be impelled inwardly towards thecenterline C/L upon 5 design. Specifically,'upon an external force beingapplied to the journal 10 by its driving motor, or the like, in adirection indicated by the arrow F, for example, the journal will pivotabout a node, or pivot point P, and assume an initial hangoff angle 0.Thus in the event there is a sensitive point associated with therotating journal or stator such as in the case of the hinge center of agyroscope, which sensitive point lies at a point shown, for example, bythe letter S in FIG. 2, a lever arm will be created corresponding to thedistance between point P and point S. The above pivoting thus creates adisplacement of the sensitive point S, which if in the form of a hingecenter of a gyroscope, will manifest itself as a gyro drift of anappreciable nature.

The above is overcome according to the journal of the present inventionshown by the reference numeral 20 in FIGS. 3 and 4, in which a first setof grooves 22 are formed to one side of the centerline C/L of thejournal and a second set of grooves 24 are formed to the other side ofthe centerline. The grooves of each set form a herringbone pattern andupon rotation. of the journal in a direction indicated by the letter Ain FIG. 3, the fluid is impelled towards the center of each set ofgrooves. Thus the radial stiffness of the bearing reaches a maximum atthese two centerlines, and, as a result, the reaction to the appliedload is redistributed to these two centerlines to create two primaryreaction points R and R The design is such that the resultant locationof pivot point P is now shifted .to the right approaching the sensitivepoint S, which also corresponds to the location of the reaction point Rfor the set of grooves 24. This significantly reduces the magnitude ofthe hangoff angle 0 because the reaction force reacting from the bearinghas more evenly distributed over the length of the shaft. As a result,the displacement of the sensitive point S is considerably reduced,minimizing the magnitude of the external force acting thereon.

It is understood that the location of the pivot point P with respect tothe sensitive point S is a matter of design depending on the particularstructure involved, and can easily be calculated utilizing basicengineering principles.

The specific pattern formed by each set of grooves may vary as long asthey impel the fluid towards the centerline of each set upon rotation ofthe journal. For example, they may take the form of a partialherringbone pattern as shown in the embodiment of FIG. 5. In thisembodiment a journal 30 is provided having a first set of grooves 32separated by a space 34, and a second set of grooves 36 separated by aspace 38. Upon rotation of the journal the grooves impel the fluidtowards the centerlines of the spaces 34 and 38 to form the reactionpoints R, and R and achieve the same effect as in the embodiment ofFIGS. 3 and 4.

As a further example of possible variations in the present invention,more than two sets of grooves may exist in which case a reaction pointwould be established for each set of grooves. Also, the location of thepivot point P and the sensitive point S do not necessarily have to bealong the axis of the journal, but may lie externally thereof along anextension of the axis. of course, still other variations of the specificconstruction and arrangement of the journal bearing disclosed above maybe made by those skilled in the art without departing from the inventionas-defined in the appended claims.

I claim:

1. A hydrodynamic bearing structure for providing a rotatable fixed-endcantilever support for one end of a rotating mass cantileveredtherefrom, comprising an inner shaft bearing member having alongitudinal axis, said inner shaft member being arranged to provide arotatable fixed-end cantilever support for oneend of the rotating masscantilevered therefrom, an outer journal bearing member extendingcoaxially with said inner bearing member, said outer journal bearingmember being arranged to resist a transverse force and a bending momenttransmitted through said inner shaft member from said rotating mass, theinner cylindrical surface of said outer bearing member being spaced fromthe outer cylindrical surface of said inner bearing member to define acylindrical bearing cavity, and a lubricating fluid disposed in saidcavity, wherein said inner shaft member surface is provided with firstand second axially spaced sets of grooves, said first and second sets ofgrooves being arranged to provide a nonuniform distribution of fluidalong the axial length of said cavity and to provide a selectivedistribution of fluid pressure along the axial length of said innershaft member surface, each said set of grooves having a plurality ofperipherally spaced grooves, each said groove having a pair of axiallyspaced symmetrically arranged groove portions, each said pair of grooveportions being arranged so as to impel said fluid axially with respectto said cavity towards a common annular zone to form at least twoaxially spaced annular zones of maximum stiffness along said journalbearing member, and wherein each groove of said first set of grooves isdisposed adjacent to and in connection with a corresponding groove ofsaid second set of grooves.

2. The bearing structure of claim 1 wherein the grooves in each set forma partial herringbone pattern, and wherein each set of grooves has anannular space portion which is disposed in an axial direction betweenthe pair of groove portions in said set of grooves, said annular spaceportion having an outer cylindrical surface.

1. A hydrodynamic bearing structure for providing a rotatable fixed-endcantilever support for one end of a rotating mass cantileveredtherefrom, comprising an inner shaft bearing member having alongitudinal axis, said inner shaft member being arranged to provide arotatable fixed-end cantilever support for one end of the rotating masscantilevered therefrom, an outer journal bearing member extendingcoaxially with said inner bearing member, said outer journal bearingmember being arranged to resist a transverse force and a bending momenttransmitted through said inner shaft member from said rotating mass, theinner cylindrical surface of said outer bearing member being spaced fromthe outer cylindrical surface of said inner bearing member to define acylindrical bearing cavity, and a lubricating fluid disposed in saidcavity, wherein said inner shaft member surface is provided with firstand second axially spaced sets of grooves, said first and second sets ofgrooves being arranged to provide a nonuniform distribution of fluidalong the axial length of said cavity and to provide a selectivedistribution of fluid pressure along the axial length of said innershaft member surface, each said set of grooves having a plurality ofperipherally spaced grooves, each said groove having a pair of axiallyspaced symmetrically arranged groove portions, each said pair of grooveportions being arranged so as to impel said fluid axially with respectto said cavity towards a common annular zone to form at least twoaxially spaced annular zones of maximum stiffness along said journalbearing member, and wherein each groove of said first set of grooves isdisposed adjacent to and in connection with a corresponding groove ofsaid second set of grooves.
 2. The bearing structure of claim 1 whereinthe grooves in each set form a partial herringbone pattern, and whereineach set of grooves has an annular space portion which is disposed in anaxial direction between the pair of groove portions in said set ofgrooves, said annular space portion having an outer cylindrical surface.